Molecular Pathogens 2024, Vol.15, No.5, 246-254 http://microbescipublisher.com/index.php/mp 246 Feature Review Open Access The Role of TAL Effectors in the Pathogenicity of Xanthomonas onLegumes Xiaoxi Zhou, Tianxia Guo Institute of Life Science, Jiyang College of Zhejiang A&F University, Zhuji, 311800, Zhejiang, China Corresponding author: 3048511772@qq.com Molecular Pathogens, 2024, Vol.15, No.5 doi: 10.5376/mp.2024.15.0024 Received: 10 Aug., 2024 Accepted: 22 Sep., 2024 Published: 09 Oct., 2024 Copyright © 2024 Zhou and Guo, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Zhou X.X., and Guo T.X., 2024, The Role of TAL effectors in the pathogenicity of Xanthomonas on legumes, Molecular Pathogens, 15(5): 246-254 (doi: 10.5376/mp.2024.15.0024) Abstract This study delves into how TAL effectors suppress plant defense responses and alter host metabolic processes, including changes in photosynthesis and hormonal pathways. It summarizes current strategies for developing disease-resistant legume crops, with a focus on the role of resistance genes (R genes) and loss-of-susceptibility (LOS) mutations. The results indicate that TAL effectors bind to specific regions of host DNA to activate susceptibility genes (S genes), thereby promoting disease progression. R genes and LOS mutations show potential in enhancing the disease resistance of legume crops. Case studies on soybeans and common beans demonstrate initial success in utilizing TAL effectors for crop improvement. This study also outlines control strategies for Xanthomonas infections, including biological control, chemical control, and integrated disease management methods, to promote the future application of TAL effectors in crop engineering and sustainable disease management. Keywords TAL effectors; Susceptibility genes; Resistance genes; Loss-of-susceptibility mutations; Disease control strategies 1 Introduction Xanthomonas is a genus of phytopathogenic bacteria known for causing a wide range of diseases in numerous economically significant crops, including legumes. These bacteria are distributed globally and are responsible for severe agricultural losses due to diseases such as blight, canker, necrosis, rot, scald, spot, streak, and wilt. The pathogenicity of Xanthomonas is largely attributed to its arsenal of virulence factors, including extracellular polysaccharides, plant cell wall-degrading enzymes, adhesins, and secreted effectors, particularly the type III secretion system (T3SS) and its associated effectors (Denancé et al., 2016). Among these effectors, Transcription Activator-Like (TAL) effectors play a crucial role in manipulating host plant cells to favor bacterial infection and proliferation (Booher et al., 2015; Xu et al., 2017). Legume crops, such as beans and peas, are vital for global food security and agricultural sustainability due to their ability to fix atmospheric nitrogen and improve soil fertility. However, these crops are susceptible to various Xanthomonas species, which can lead to significant yield losses. For instance, Xanthomonas axonopodis pv. manihotis, which affects cassava, employs TAL effectors to promote bacterial growth and symptom formation (Cohn et al., 2016). Similarly, other Xanthomonas species infecting legumes utilize TAL effectors to manipulate host gene expression, thereby facilitating infection and disease progression (Hutin et al., 2015; Denancé et al., 2018). This study will provide a comprehensive overview of the role of TAL effectors in the pathogenicity of Xanthomonas on leguminous crops. It will analyze the structure and function of TAL effectors in Xanthomonas and further explore the mechanisms by which TAL effectors regulate host gene expression to promote disease. Additionally, it will investigate the evolutionary dynamics of TAL effector genes and their impact on pathogen diversity and virulence. The study highlights the importance of TAL effectors in Xanthomonas-legume interactions and discusses potential strategies for developing resistant legume varieties to mitigate the impact of these pathogens on agriculture. 2 TAL Effectors: Structure and Function 2.1 Structural features of tal effectors Transcription activator-like (TAL) effectors are a class of proteins secreted by Xanthomonas species through the
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